Fragility functions for corroded reinforced concrete columns

Fragility functions for structural members play an important role in the FEMA P-58 methodology for the seismic performance assessment of structures. In this study, fragility functions were developed for aged reinforced columns with corroded reinforcing bars. To this end, an experimental database containing 120 specimens subjected to repeated cyclic loads was compiled from 20 previous studies. The experimental specimens were categorized into three groups: no corrosion damage (NCD), low corrosion damage (LCD), and high corrosion damage (HCD). These damage states were identified by experimental hysteretic responses in terms of the drift angle, which are linked to common methods of repair, including structural repair, structural enhancement, and component replacement. The obtained drift angles were used to fit the log-normal fragility functions of the NCD, LCD, and HCD columns. The effect of reinforcement corrosion was examined by comparing the fragility functions of uncorroded and corroded columns. According to the principles suggested by FEMA P-58, the developed fragility functions were mostly judged to have a high level of quality. The fragility medians of the corroded columns showed a clear decreasing trend along with an increasing degree of corrosion damage. However, the corrosion of the reinforcing bars had a limited effect on the fragility dispersion. The maximum differences in the exceedance probability were calculated by comparing the fragility curves for the LCD and NCD columns, which were greater than 20 % for all concerned damage states. For the HCD columns, the corrosion of the reinforcing bars led to the maximum difference in the exceedance probability, even beyond 50 %, compared to the results for the NCD columns. The above results reveal the significant effect of the corrosion of the reinforcing bars. The specific fragility functions developed for the corroded reinforced concrete columns will facilitate the seismic loss and resilience assessment of aging reinforced concrete building structures.